The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2002-286170, filed on Sep. 30, 2002, the contents of which is herein expressly incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a clinch mechanism for a stapler that drives a staple through stacked sheets of paper with a hammer and clinches the piercing legs of the staple to hold the paper together, and an electric stapler using this clinch mechanism.
2. Description of Related Art
An electric stapler, which automatically drives a staple into an inserted stack of paper, is suitably used for handling a large number of paper or when paper handling is frequently necessary. Commercially available electric staplers include both battery-powered type and AC-powered type. While the former has the advantage of being cordless, the latter is more preferable in that it is free of battery exhaustion; also, the latter can be constructed smaller and more lightweight because it need not accommodate many batteries for supplying power necessary to staple multiple paper sheets.
FIG. 12 illustrates an AC-powered electric stapler shown in Japanese Patent Laid-Open Publication No. 2000-153470 (reference A). A motor 8 rotates a crank gear 25 and turns a crank rod 26, thereby moving a hammer 3 at the distal end of the rod 26 downward to drive a staple accommodated in a staple holder 30 into a stack of paper placed on a clinch plate 32. The legs of the staple penetrated through the stack are bent by the clinch plate 32, thus holding the paper together.
The clinch plate 32 has a guide groove so as to bend legs of driven staples inwards to face each other. This bending of staples by the clinch plate 32 deforms the legs of staples in an arc, so the problem is that the thickness of the stack of paper in the stapled portion is larger than the other portions. Also, this structure with the clinch plate 32 has a drawback that the bending is achieved with less certainty particularly when the stack is thick. In order to staple multiple paper sheets, staples with longer legs are necessary; one requirement here is to clinch the driven staples in a non-overlapping manner so that the clinched part will not cause an increase in the thickness of the stacked paper.
FIG. 13A and FIG. 13B illustrate the construction of a stapler clinch mechanism shown in Japanese Patent Laid-Open Publication No. Hei 10-118956 (reference B), which bends long-legged staples in a non-overlapping manner. Two movable clinchers 53a, 53b are arranged in grooves 45a, 45b that are respectively formed between stationary walls 44a, 44b and receiving plates 43a, 43b having different thicknesses. The receiving plates 43a, 43b are formed with guide slopes 48 at locations in point symmetry around the center O therebetween for receiving legs 52a of a staple 52. The staple legs 52a are guided in opposite directions by the guide slopes 48 into the grooves 45a, 45b and clinched by the clinchers 53a, 53b. 
Driving staples with long and wide apart legs into multiple sheets requires a large power supply with uniform pressure application.
The conventional electric stapler of the above reference A is structurally incapable of applying large and uniform pressure with the hammer on the staple legs. The clinch plate cannot bend large-sized staple legs; a clinch mechanism is necessitated for heavy duty stapling tasks.
The conventional clinch mechanism of the above reference B, however, has a drawback that staple legs can easily be deformed in a central part because of the symmetric design in which the movable clinchers are accommodated in the grooves formed by oppositely arranged plates with different thicknesses. Thus stable clinching may not be achieved in repeated use applications.
An object of the present invention is to provide an improved clinch mechanism for a stapler that bends staple legs in a non-overlapping manner, and an electric stapler using this clinch mechanism.
To achieve the above object, the present invention provides a clinch mechanism for a stapler that pushes and drives a staple out of a staple magazine into a stack of paper by a lowering motion of a hammer, and clinches legs of the staple that has penetrated the paper inward to hold the paper together, including: a pair of base plates arranged parallel with a spacing therebetween that conforms to a direction in which the legs of the staple that has penetrated the paper are oriented; a thin-plate partition forming equally spaced gaps on both sides thereof by halving the spacing between the pair of base plates, the partition including a pair of protruding pieces on an top side thereof respectively corresponding to each of staple legs, which protruding pieces are bent in opposite directions at a preset angle to form slanted faces that partly close the equally spaced gaps, respectively; a pair of clinch plates rotatably arranged inside the equally spaced gaps; and a clinch arm for rotating the pair of clinch plates simultaneously with the lowering motion of the hammer.
With this clinch mechanism, the legs of the staple that has penetrated the paper are driven onto the top side of the partition and guided into the equally spaced gaps by the slanted faces of the pair of protruding pieces. The pair of clinch plates disposed in these gaps are then turned by the clinch arm so as to clinch the staple legs to hold the paper together. The staple legs are first bent in opposite directions by the pair of protruding pieces before being clinched by the clinch plates, so that they do not overlap each other and the clinched part of paper is prevented from causing an increase in the thickness of the stacked paper.
The present invention also provides an electric stapler that pushes and drives a staple out of a staple magazine into a stack of paper by a lowering motion of a motor-driven hammer, and clinches legs of the staple that has penetrated the paper inward to hold the paper together, including: a support stand having a pair of upright walls facing each other; a magazine holder holding the staple magazine, arranged between the upright walls, pivotable around an axis at a rear end, and biased upwards; a staple firing assembly including a structure for moving up and down the hammer along a vertical staple firing line at a front end of the support stand and a structure for lowering the staple magazine; a clinch mechanism having a clinch plate disposed below the staple firing line for bending staple legs; a pair of wheel gears attached to the upright walls of the support stand, respectively, and driven by the motor synchronously; a swing arm bridging across the upright walls, turned by the pair of wheel gears to drive the staple firing assembly around a shaft that is biased downwards by a pair of springs; and a clinch arm turned by the pair of wheel gears to drive the clinch mechanism.
With this electric stapler, a large pressure is applied equally on both legs of staples because of the configuration in which the staple firing assembly is driven by the swing arm that is turned by the pair of wheel gears driven by the motor. Staples with long and wide apart legs are thus driven successfully into a thick stack of paper. The pair of wheel gears also rotate the pair of clinch plates of the clinch mechanism through the clinch arm simultaneously with the operation of the staple firing assembly, ensuring clinching of long staple legs.
In this electric stapler constructed as above, the clinch mechanism includes a pair of base plates arranged parallel with a spacing therebetween that conforms to a direction in which the legs of the staple that has penetrated the paper are oriented; a thin-plate partition forming equally spaced gaps on both sides thereof by halving the spacing between the pair of base plates, the partition including a pair of protruding pieces on an top side thereof respectively corresponding to each of staple legs, which protruding pieces are bent in opposite directions at a preset angle to form slanted faces that partly close the equally spaced gaps, respectively; and a pair of clinch plates rotatably arranged inside the equally spaced gaps. This makes it possible to bend the staple legs so that they do not overlap each other.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.